This application claims the priority of German Patent Application, Serial No. 199 46 122, filed Sep. 20, 2000, the subject matter of which is incorporated herein by reference.
The present invention relates to a gripper of a liftable and lowerable load-carrying apparatus for grabbing containers from above.
German Patent No. 42 29 215 A1 discloses a gripper for grabbing loads from above. The gripper includes a frame composed of longitudinal beams and interconnecting cross beams and is connected to a hoist via an eyelet. Disposed on each of the cross beams is a pair of gripper elements which are spaced from one another at a distance substantially corresponding to the length of the cross beam. As a consequence, the distance between the gripper elements is great in relation to the dimensions of the gripper elements with respect to width, length, and thickness. Each gripper element has two hook members positioned in a common vertical plane and including hook ends facing away from one another. The hook ends adjacent areas of both hook members are in confronting relationship and adjoin one another, when the gripper element is in its ready position. The gripper elements extend vertically downwards and engage in complementary container openings, when the frame is placed upon the container, whereby the container openings have a slotted configuration in the sidewall of the container. This conventional gripper is predominantly intended for use with standardized containers with open top and vertical sidewalls that have in the upper rim zone the container openings which extend into the sidewall. The hook members of each gripper element are pushed apart into a gripping position by a rod assembly for grabbing behind the rim of the slotted opening.
A drawback of this conventional gripper is its relatively complex structure and the need to assemble many single components.
German Pat. No. DE 42 29 346 describes a vertically adjustable gripper for system containers, having two cross beams which each have a pair of gripper elements that are movable transversely to the lift direction.
It is thus an object of the present invention to provide an improved gripper, obviating the afore-stated drawbacks.
In particular, it is an object of the present invention to provide an improved gripper which is simple in structure and comprised of only few individual parts that are cost-efficient to fabricate, and yet is reliable in operation.
These objects, and others which will become apparent hereinafter, are attained in accordance with the present invention by providing a frame placed from above onto a container and having spaced-apart cross beams, each cross beam defining a longitudinal direction and having at least two gripper elements spaced from one another at a distance which is greater than a dimension of the gripper elements, with each gripper element depending from the cross beam for insertion through a container opening when the frame is placed on the container, said cross beam being made of two sheets which are movable relative to one another in the longitudinal direction, with one of the sheets having one of the gripper elements and the other one of the sheets having the other one of the gripper elements, with the two gripper elements movable in opposite direction to one another in the longitudinal direction of the beam between a ready position and a gripping position.
In accordance with the present invention, each cross beam has thus at least a pair of gripper elements, whereby each pair of gripper elements is linearly movable in opposition to one another in longitudinal direction of the cross beam. Thus, each cross beam has at least two gripper elements spaced from one another at a relatively great distance. The gripper elements, e.g., mounted to a carrier element, are moved into the gripping position by respectively linearly shifting the carrier elements until the gripper elements engage underneath the respective holding elements on the container. For grabbing, the gripper elements of each pair are displaced until bearing upon the edges of the container opening. This configuration is simple in construction and requires only a small number of individual components.
According to the present invention, each cross beam is made of two sheets which are movable in the longitudinal direction, wherein one of the sheets has one of the gripper elements and the other one of the sheets has the other one of the gripper elements, with the two gripper elements movable in opposite direction to one another in the longitudinal direction of the cross beam. Thus, the sheets can be advantageously manufactured in almost any contour in a simple and cost-efficient manner.
The construction of the gripper can be further simplified when the length of the cross beam is variable by adjusting the two sheets relative to one another in synchronism for moving the gripper elements between the gripping and ready positions. The gripper elements are hereby securely fixed to the cross beams.
To ensure the displacement of the sheets in the longitudinal direction, it is proposed to provide each of the sheets with a circular opening for receiving a bolt in a direction transversely to the longitudinal direction, and with an elongate hole spaced from the opening in longitudinal direction, with the bolt received in the opening of one of the sheets engaging the elongate hole of the other one of the sheets. In this manner, the guidance in the longitudinal direction is easy to make while yet reliable in operation.
A more secure grabbing operation by the gripper is realized when according to another feature of the present invention, each of the gripper elements is provided with two hook members, with one of the hook members located on one of the sheets and the other one of the hook members located on the other one of the sheets. Suitably, the hook members of each gripper element point away from one another, so that the hook members are able to grab from underneath the container opening on opposite side edges.
A reliable movement of the gripper elements from a spaced-apart disposition into an overlapping disposition can be ensured by overlapping the hook members of each gripper element with one another in a direction transversely to the longitudinal direction when the gripper element is in the gripping position and the hook members are moved apart. The displacement of the hook elements is thus restricted to an extent that prevents the formation of a gap between the hook elements in transverse direction when the hook members are pushed apart, and eliminates the risk that the hook members interlock.
According to another feature of the present invention, each of the sheets is formed in one piece with the hook member, suitably by cutting from sheet metal, in particular through a laser cutting process. In this manner, the manufacturing process is simplified.
To prevent a penetration of thin container walls, ribs or ridges between two hook members when the frame is incorrectly positioned upon the container, one of the hook members may have a lower end which is so configured as to cover a gap formed between the hook members. This may be realized by simply bending the lower end inwards and cutting this end at an angle so that an edge is created which covers the gap.
Suitably, the hook members of each gripper element so cover one another when pushing the hook member together, as viewed transversely to the longitudinal direction, as to form a downwardly tapered entry element for insertion into the container opening. In this manner, the insertion of the gripper elements into the container is simplified and reliable, and the gripper elements exhibit a hook-free shape.
According to another feature of the present invention, the longitudinal beams have ends, with the bolts arranged at the ends. The bolts may hereby be formed onto the ends of the longitudinal beams to simplify the overall construction.
In order to suit the gripper to containers of different width, the parallel longitudinal beams are each telescopically changeable in length.
According to another feature of the present invention, a movement of the hook members is ensured by rotatably attaching rollers to the bolts for placement on a rim of the container, thereby reducing the frictional resistance.